Learning Python, 3rd Edition

Chapter 23. Class Coding Basics

Now that we’ve talked about OOP in the abstract, it’s time to see how this translates to actual code. This chapter and the next will fill in the syntax details behind the class model in Python.

If you’ve never been exposed to OOP in the past, classes can seem somewhat complicated if taken in a single dose. To make class coding easier to absorb, we’ll begin our detailed exploration of OOP by taking a first look at some basic classes in action in this chapter. We’ll expand on the details introduced here in later chapters of this part of the book, but in their basic form, Python classes are easy to understand.

Classes have three primary distinctions. At a base level, they are mostly just namespaces, much like the modules we studied in Part V. But, unlike modules, classes also have support for generating multiple objects, for namespace inheritance, and for operator overloading. Let’s begin our class statement tour by exploring each of these three distinctions in turn.

Classes Generate Multiple Instance Objects

To understand how the multiple objects idea works, you have to first understand that there are two kinds of objects in Python’s OOP model: class objects, and instance objects. Class objects provide default behavior, and serve as factories for instance objects. Instance objects are the real objects your programs process—each is a namespace in its own right, but inherits (i.e., has automatic access to) names in the class from which it was created. Class ...